The present disclosure relates to a wet brake.
Japanese Unexamined Patent Application Publication No. 2007-120559 mentions the well-known art for wet brakes. A wet brake mentioned in the above-mentioned publication includes a plurality of friction plates, a plurality of brake plates, a thrust member, and a parking brake piston. The plurality of friction plates are supported by a spline member that is secured to an inner periphery of a reduction gear box. The friction plates are movable in an axial direction of the spline member, but not rotatable. The plurality of the brake plates is supported by a spline ring that is splined to an outer periphery of a sun gear axle. The brake plates are movable in the axial direction of the spline member, but not rotatable. Each brake plate is interposed between any two adjacent friction plates. The thrust member has an annular plate shape, and is configured to contact with an innermost one of the friction plates with respect to a vehicle to which the wet brake is mounted. The parking brake piston is disposed inward of the thrust member, and is configured to push the thrust member outward with reference to the vehicle in response to a pressing operation of the parking brake. The thrust member is moved to press the friction plates to the brake plates, which applies a brake to the sun gear axle.
For example, in a forklift truck including a mast and a mast support provided to a bottom part of the mast, a wet brake may be mounted to the mast support in such a manner that a mounting groove formed in an outer peripheral surface of a housing of the wet brake receives the mast support of the mast. In this wet brake, one way of achieving a desired braking force is to expand an outer diameter of a piston included in the wet brake to increase an area of contact between the piston and a brake disc that is pushed by the piston. However, this way requires extending a distance between the mounting groove and a rotary shaft that is disposed in the piston to secure a necessary wall thickness of the housing, which results in a dimensional change of the mast support (i.e., a mounted object) and therefore a design change of the mast itself.
The present disclosure, which has been made in light of the above described problem, is directed to providing a wet brake wherein a change in an outer diameter of a piston is allowed without making any influence on design of a mounted object.